The present invention relates to the general field of fluid transport pipes, in particular subsea pipes, lying on the seabed or providing the seabed-to-surface connection for the transfer of hydrocarbons, for example oil and gas, from subsea production wells.
More specifically, the invention relates a process for lining such pipes made of carbon steel to clad them internally with a corrosion-resistant alloy layer (for example Inconel®).
Some subsea hydrocarbon transport pipes, and in particular pipes providing a seabed-to-surface connection, called risers, are internally lined with an alloy steel layer typically between 2.5 mm and 5 mm thick to create a corrosion barrier and to improve the mechanical and chemical properties of the pipe.
Pipes lined internally with such a corrosion-resistant alloy layer are generally obtained by mechanically bonding the alloy layer (also called liner) to the pipe body. At each end of the pipe, the corrosion-resistant alloy layer is connected to the pipe body by overlapping weld seams, the filler metal usually being Inconel® based.
More precisely, the known liner processes of the prior art propose to force the corrosion-resistant alloy layer into the pipe, to deposit a weld bead at each end of the pipe to provide support at the ends of the alloy layer, and then to perform surface machining of the weld bead to the internal diameter of the pipe.
For example, document WO 2015/087162 discloses a process for connecting two pipe elements, each with a corrosion-resistant alloy liner. According to this invention, it is provided to carry out a finishing machining of each end of the pipe to form bevels for the deposition of a weld bead intended for assembling the pipe elements together, then to machine the end portions of the liner of each pipe element in order to deposit a weld overlay. The weld overlay is then machined to the internal diameter of the pipe.
However, such lining processes have certain disadvantages, particularly in terms of the fatigue strength of the lined pipe thus obtained. Indeed, when the pipe is subjected to significant fatigue, discontinuity at the interface between the corrosion-resistant alloy liner and the weld overlay can initiate cracks that may propagate through the thickness of the pipe until it causes the fatigue failure of the steel it contains.